[mlir][ArmSME] Fix get_tile_id type in zero lowering

The arm_sme.get_tile_id op returns a scalar integer but the arm_sme.zero
op lowering incorrectly uses the element type, which could be
floating-point.

Reviewed By: awarzynski, benmxwl-arm

Differential Revision: https://reviews.llvm.org/D159080